Even more interesting to hear they either retained their grip or possibly gained some grip as the tread wore down (in the absence of significant prior heat cycling as you point out). How much tread would you say you ended up with at the end of the short or the longer races? In other words, how close do you think the tires were to being corded?

When the tread was almost like a holograph is where they were quickest and were only laps away from cording.They could have a fair bit of cording and not slow down as much as you would think they would.